Colloids and Surfaces
A: Physicochemical and Engineering Aspects 183-185 (2001) 563 – 574
Influence of sodium dodecyl sulfate on structure and
rheology of aqueous solutions of the nonionic surfactant
tetraethyleneglycol-monododecyl ether (C
12
E
4
)
Florian Nettesheim
a
, Johannes Zipfel
a
, Peter Lindner
b
, Walter Richtering
c,
*
a
Institut fu ¨r Makromolekulare Chemie, Uniersita ¨t Freiburg, Stefan -Meier -Str. 31, D-79104 Freiburg i. Br., Germany
b
Institut Laue -Langein, Grenoble, France
c
Institut fu ¨r Physikalische Chemie, Christian -Albrechts -Uniersita ¨t zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
Abstract
The influence of the ionic surfactant sodium dodecylsulfate (SDS) on structure and rheology of the lamellar phase
of the nonionic surfactant tetraethyleneglycol-monododecyl ether (C
12
E
4
) at intermediate concentrations was investi-
gated by means of small angle light and neutron scattering (SALS, SANS) and rheometry. The long range
orientational order increased with added SDS as expected and the Caille ´ parameter was obtained from SANS data.
The shear viscosity increased when SDS was added. Rheo SALS experiments revealed the shear induced formation
of multilamellar vesicles (MLV or ‘onions’) and the MLV size decreased not only in shear thinning but also in the
shear thickening region. The increase in Bragg scattering intensity along the flow direction as observed in the
rheo-SANS experiments also revealed the increase in MLV volume fraction in the shear thickening regime. The SANS
data further showed a decrease in layer spacing with increasing shear which indicates that water is squeezed out of
the vesicles. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Sodium dodecyl sulfate; Sans data; Vesicles
www.elsevier.nl/locate/colsurfa
1. Introduction
Concentrated aqueous surfactant solutions dis-
play a variety of structural features and are there-
fore systems of considerable interest for industrial
applications as well as for model systems used in
fundamental research. Often a lamellar
mesophase is found in a wide range of concentra-
tion and temperature. The phase behaviour of
nonionic surfactants of the C
n
E
m
type with the
general formula CH
3
(CH
2
)
n -1
(OCH
2
CH
2
)
m
OH in
aqueous mixtures has been investigated for many
different systems focusing on aspects like the alkyl
chain length and the size of the surfactant head-
group [1,2]. The influence of shear on the struc-
ture of complex fluids caught a lot of attention in
the last years [3–7]. Particular attention was paid
to lyotropic lamellar phases exhibiting interesting
behaviour under shear as first described by Roux
and coworkers [8,9]. One is the flipping of aligned,
planar lamellae [10 – 17] and the second concerns
* Corresponding author.
E-mail address: richtering@phc.uni.kiel.de (W. Richtering).
0927-7757/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII:S0927-7757(01)00513-1